A pair of shackles of the sort used during the cruel "Middle Passage" from Africa to the Americas. Images of such shackles appear in numerous early anti-slavery books and tracts. For specific examples, see: "An Abstract of the Evidence," London 1791; Lydia Maria Child's "Appeal in Behalf of that Class of Americans called Africans," Boston, 1833; and Lorenzo Dow, "Slave Ships and Slaving," Massachusetts, 1927.